Question

A sample of a radioactive substance decayed 11% over the course of 3 weeks. How many grams were in the sample originally if 30.26 grams of the substance were remaining after the 3 weeks?

Answer 1

The original amount of a radioactive substance that decayed by 11% can be found by dividing the remaining amount by the remaining percentage as a decimal. For 30.26 grams left after decay, the original amount was approximately 34.00 grams.

Step-by-step explanation:

To find the original amount of a radioactive substance given its remaining amount after decay, we can use the concept of decay percentage. In this scenario, the substance decayed by 11%, meaning that 89% of the original amount is left. To find the original amount, we simply divide the remaining amount by the percentage that is left as a decimal. Here's how the calculation is performed step-by-step:

1. Convert the percentage remaining to a decimal: 89% = 0.89.
2. Divide the remaining amount by the decimal: 30.26 grams / 0.89 = original amount.
3. Perform the division to find the original amount: approximately 34.00 grams.

Therefore, the original amount of the radioactive substance was about 34.00 grams.

Answer 2

34 grams

Step-by-step explanation:

If the remaining sample has 30.26 grams of radioactive substance, and 11% of it decayed, that means that 30.26 grams is 89% of the original. Let the original be x.

30.26=0.89x

Multiply both by one hundred

3026=89x

Divide both by 89

34=x

x=original, so the original was 34 grams.